This invention relates to an aqueous cleaning composition and to a method of using same to clean substrates. More particularly, this invention relates to an alkaline, aqueous cleaning/degreasing composition containing a particular combination of surfactants and to a method of using such composition to remove industrial-type soils from substrate surfaces.
Many industries, such as, for example, automobile parts repair and replacement services and the like, require that component mechanical parts be cleaned prior to inspection, repair, or replacement thereof. Generally, such parts have been exposed to various contaminants such as dirt, grease, oil, ink and the like, which must be removed for effective repair or service.
A variety of metal cleaners have been used to clean such mechanical parts. For example, solvent-based metal cleaners have been used which contain either halogenated or non-halogenated hydrocarbons. Aqueous-based, highly alkaline detergent systems have also been used to clean metal parts. However, the use of such solvent-based or aqueous-based cleaners has raised environmental and/or worker safety concerns.
For example, although halogenated hydrocarbon solvents such as chlorofluorocarbons (CFCs), trichloromethane, methylene chloride and trichloroethane (methyl chloroform) have been widely used in industry for metal cleaning, the safety, environmental and cost factors associated with their use coupled with waste disposal problems are negative aspects of the use of such solvents. A world-wide and U.S. ban on most halogenated solvents is soon in the offing by virtue of the Montreal Protocol, Clean Air Act and Executive and Departmental directives.
Non-halogenated hydrocarbon solvents such as toluene, Stoddard solvent and like organic compounds such as ketones and alcohols are generally flammable and highly volatile and have dubious ability to be recycled for continuous use. These factors, along with unfavorable safety, environmental and cost factors, make the non-halogenated hydrocarbon solvents unattractive for practical consideration. For example, the most useful organic solvents, classified as volatile organic compounds (VOCs), pollute the atmosphere, promote formation of a toxic zone at ground level, and add to the inventory of greenhouse gases.
Aqueous cleaning systems have been developed to overcome some of the inherent negative environmental and health aspects associated with the solvent-based cleaning systems. Unfortunately, aqueous cleaning systems also have drawbacks.
For example, aqueous cleaners containing sodium hydroxide or organic solvents such as alkanolamine, ethers, alcohols, glycols and the like, tend to be exceedingly alkaline, i.e., having pHs of 13 and above. These exceedingly alkaline aqueous solutions are highly corrosive to metal surfaces, highly toxic and can be dangerous to handle, thus requiring extreme safety measures to avoid contact with the skin. The organic solvent-containing aqueous cleaners have the toxicity and environmental problems discussed previously herein.
Although the exceedingly alkaline aqueous cleaners have the aforementioned drawbacks, it has been most difficult to obtain an aqueous detersive solution which has a moderate pH (i.e., less than about 12.0) and which is effective in removing grease and oil contaminants from substrates, e.g., metal engine parts, and which would not be corrosive to metal substrates.
A primary object of this invention is to provide an alkaline aqueous cleaning composition which has a moderate pH and which effectively removes industrial-type soil contaminants from substrates.
Another object of this invention is to provide an alkaline aqueous cleaning composition having a moderate pH and which effectively removes industrial-type soil contaminants from a metal substrate without being excessively corrosive to the metal substrate.
A further object of this invention is to provide an alkaline aqueous cleaning composition having a moderate pH and which effectively removes industrial-type soil contaminants from a substrate, wherein the cleaning composition is not irritating to human skin and is less toxic upon accidental ingestion than are organic-based solvent systems.
Still another object of this invention is to provide a method of cleaning substrates by means of an alkaline aqueous cleaning composition having the properties described in the foregoing objects.
These and other objects which are achieved according to the present invention can be readily discerned from the following description.